Prescription sunglasses cost basically what regular prescription glasses cost. The additional charge for the tint is very small. If you go for polarized or transitions lenses it can add up. What did your regular glasses cost?

I have progressive bifocal lenses in my regular glasses and my general us sunglasses. They run about the price you said in the OP. I just use a single vision prescription for my riding glasses, so they cost a good bit less for the lenses.